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The Finnish Experience With a National CVD Event Register During 1991-2003 - Dr. Veikko Salomaa
There are two types of population-based cardiovascular disease registers in Finland. The FINAMI register (1,2) is based on detailed reviewing of hospital documents, death certificates and autopsy reports following the tradition of the WHO MONICA Project. It is operating in four geographical areas of Finland and aims to register every CHD event in monitored populations. The register is planned for scientific research and has standardized data collection and quality control procedures. Therefore, the data it produces can be considered as accurate and reliable. The limitation is that the register is rather laborious and expensive to maintain and can cover only a small fraction of the country. The other type of CVD register is based on record linkage of administrative data, i.e., the National Hospital Discharge Register and the National Causes-of-Death Register (3,4). These country-wide computerized registers cover every hospitalisation in Finland and all deaths of permanent residents of the country. They can be linked together on the basis of the personal ID code, unique to every resident of Finland. Data on CHD and stroke events during 1991-2003 based on the record linkage of these administrative registers have been placed in the Internet, where they are freely available. The database has a user-friendly interface, which allows easy examination of event rates, in-hospital and out-of-hospital case fatality as well as one-year prognosis by age, sex, and hospital district. The strength of the administrative registers is that they cover the whole country and all age groups and provide data on large numbers of CVD events at a modest cost. For example, our database for the period 1991-2003 includes 333 015 CHD and 304 863 stroke events. On the other hand, only a limited standardization and quality control are possible for the administrative data. However, the more detailed FINAMI register can be used as a validation instrument for the country-wide administrative CVD-register. Validation studies have shown that the sensitivity and positive predictive value of CVD diagnoses in the Finnish administrative registers are reasonably good (5). Similar national CVD registers based on administrative data exist also in Sweden and Denmark. In the framework of the NORDAMI Project we are currently establishing common definitions for CVD events in these registers. The goal is that in the near future reasonably comparable data on the incidence and case fatality of CVD events in these three Nordic countries become freely available at a common website. At the European Union level, the EUROCISS (=European Cardiovascular Indicators Surveillance Set) Project aims to identify a set of CVD indicators, for which monitoring is both needed and feasible in the whole EU (6).
Figure 1 demonstrates the trends in the incidence of first ever MI events in Finland during 1991-2003, based on the administrative data. The decline was steep until 1997 and somewhat slower after that, which is likely to be due to the widespread adoption of troponins as the markers of myocardial injury. We have analyzed the effects of changing diagnostic criteria on the event rate estimates of MI using data from the FINAMI register (2). The findings suggested that the estimates of hospitalised CHD events increased by 15% among men and 38% among women aged 35-74 years with the adoption of troponins and the latest diagnostic criteria (7). Somewhat surprisingly, the additional cases identified by troponins and the new criteria had worse prognosis than those cases, which were definite MIs also according to the WHO MONICA criteria based on enzymatic markers of myocardial injury.
In conclusion, a country-wide CVD register based on administrative data and a geographically limited but more rigorously standardized register are used in a complementary manner in Finland. Together they provide a fairly good picture on the occurrence, case fatality and prognosis of CVD events in the country.
Figure 1. The age-standardized incidence of first MI events in 1991-2003 in Finland. The annual average decline was 4.9% (95% CI -5.2% to -4.5%) from 1991 to 1997 and 2.1% (95% CI -2.5% to -1.8%) from 1998 to 2003 among men. The respective changes among women were -5.2% (95% CI -5.8% to -4.7%) and -2.1% (95%CI -2.7% to -1.5%).